1. Field of the Invention
The invention relates to an electric motor-operated actuator for a motor vehicle lock, e.g. door lock, rear hatch lock, hood lock.
2. Discussion of Related Art
A conventional electric motor-operated actuator for a motor vehicle lock is disclosed in U.S. Pat. No. 4,518,181 in conjunction with a comprehensive description of a motor vehicle side door lock. This patent points out that an actuator pulley is any functional component which has a corresponding actuator function. This also applies in the present case. In the prior art, as alternatives, there is one actuator pulley on the one hand for radial movements and one actuator cylinder with the cylinder axis as the axis of rotation for axial movements.
The known electric motor-operated actuator for a motor vehicle lock includes a control crank which runs in a spiral in the actuator pulley, by a notably small drive output of the electric drive motor. In end positions, which correspond to the inner stop or the outer stop of the control crank, manual switching between the operating states "unlocked" and "locked" can be done without hindrance. The number of components is small, both in radial and axial movement of the control lever by the control crank. The stop running against the guide element journal) can trigger the shutoff of the electric drive motor (block mode).
Because the control crank extends between the inner stop and the outer stop via a guide channel which is closed at a minimum of more than 360.degree. for the journal of the control lever and is closed only in the overlap between the inner stop and outer stop with a transverse channel which extends radially or axially, to enable manual switching, the actuator itself does not require a tilt spring which loads the control lever. In this way, motor output becomes especially low. In any case, in this prior art, a tilt spring, which is designed at least as a weak spring, is feasible for the control lever in order to achieve defined operating states.
The closed guide channel, which is formed by the control crank over the latter's entire length, disadvantageously only permits manual switching in the end position, and precludes manual switching in between. When the electric drive motor fails, the control lever is blocked. Since the rise of the control crank over 360.degree. is relatively low, when a conventional small diameter of the actuator pulley of a few centimeters must be accepted, in conventional overall gearing down, the actuator is self-locking and therefore cannot be turned back by hand.
The above described problem has already been recognized in the above explained prior art. A second embodiment includes a construction in which the control crank extends between the inner stop and the outer stop likewise again over a minimum of more than 360.degree.. However, the control crank is no longer made as a closed guide channel for the journal of the control lever, but as the outer and inner guide cams. The choice of radii of the outer and inner guide cams is made such that only an angular area of roughly 180.degree. each has a changing radius with which the journal is then displaced radially to the inside or to the outside. These areas on the outer guide cam and on the inner guide cam do not overlap one another. By means of the respective guide cam on which the journal is held in a defined manner by a tilt spring, the journal is moved to the inside or outside by turning the actuator pulley until the tilt spring turns over and shifts the control lever into the respective other operating state. This shifting movement, not the journal striking the inner stop or the outer stop, shuts off the drive motor by means of a switching contact. Afterwards, a reset spring takes effect by acting in both directions and always returning the actuator pulley with the control crank to a middle position in which the journal on the control lever is located in the widest section of the control crank. In the middle position, manual switching between the operating states "unlocked" and "locked" is easily possible.
In a second embodiment of the above-described prior art, the actuator is not self-locking, but can be reset. The reset spring which is present for resetting, however, requires a significantly increased drive output of the electric drive motor. Turning the actuator pulley back by hand when the electrical drive motor fails is not described, but is generally not necessary either due to the reset spring. This second prior art embodiment, in addition to the high drive output of the electric drive motor, has the further disadvantage that the control lever actually turns over under the action of the tilt spring. Therefore, the control lever is not guided beyond the tilt point of the tilt spring by the control crank which is made as a closed guide channel. The noise generated is thus higher than in the first prior art embodiment.